Voltage regulating device with an ionizable medium temperature responsive to load demand



March 1965 J. w. DRENNING ETAL 3,

VOLTAGE REGULATING DEVICE WITH AN IONIZABLE MEDIUM TEMPERATURE RESPONSIVE TO LOAD DEMAND 3 Sheets-Sheet 1 Filed Dec. 22, 1959 5 2 u A I! u w/ B u 6 v M a 3 LII J. w. DRENNING ETAL 3,176,216

March 30, 1965 VOLTAGE REGULATING DEVICE WITH AN IONIZABLE MEDIUM TEMPERATURE RESPONSIVE TO LOAD DEMAND 3 Sheets-Sheet 2 Filed D90. 22, 1959 VOL'NAGE. IN K ILOVOLTS LOA D POWER 5U P FLT INVENTORJ. Jam/ Mass/mum Jaw/Y 5, 77100705 8% March 30, 1965 J. w. DRENNING ETAL $176,216

VOLTAGE REGULATING DEVICE WITH AN IQNIZABLE MEDIUM TEMPERATURE RESPONSIVE T0 LOAD DEMAND United States Patent VULTAGE REGULATlNG DEVHQE 'vVl'll-l AN l abl- EZAELE lviEDlUM TEMPERATURE Pshl ait ill lhllll T0 JLQAD DEMAND John W. Drenning, Baltimore, Md, and John B. Thomas, Plainshoro, N..l'., assignors to Kcppers Company, inc, a corporation of Delaware Filed Dec. 22, 1959, Eser. No. 861,341 2 (Ilaims. (til. 323-23) This invention relates to voltage regulator and voltage reference devices. More particularly, this invention relates to those regulating and reference devices employing high voltage gas discharge called a corona discharge.

The corona discharge is a corona discharge device is conventionally established by providing an asymmetrical positive and negative electrode geometry therein between which there is disposed a gas. A voltage is applied across the electrode structure such that large voltage gradients are established in the gas adjacent one of the electrodes. As the voltage across the electrode structure is increased beyond a critical value called cornea onset, the gas becomes ionized as a result of the large voltage gradients. The ionization of the gas causes a current flow through the gas and between the positive and negative electrodes. The gas employed in a corona discharge device is generally selected so that current how and applied voltage iollows a relationship wherein the electrode voltage is substantially constant and independent of the current flow Within the operating voltage range of the electrode arrangement. in the typical or conventional structure of corona discharge devices, there are inherent detectable voltage changes at the electrode with a change in current. These detectable changes are conveniently expressed in terms of the percentage of regulation of the device.

These corona devices are employed as voltage regulating tubes vand are designed to operate at various difierent useful values of voltage.

conventionally, corona voltage regulating devices are connected into a rectifier circuit and operate as shunt type regulating devices. The load is usually connected in parallel with the voltage regulator and is subjected to the same voltage which, to achieve optimum performance, should desirably be substantially constant and independent of the current drawn.

Gne of the major limitations of these prior voltage regulating devices is the inherent detectable changes in voltage at different values of curent flow. At conventional operating temperatures (up to 150 C.) the relationship between regulator vol-tage and current is such that in the typical regulator tube, the operating range is approximately 2-10 percent of the nominal regulated voltage at the electrode. The percentage of variation from the nominal regulation varies with the voltage to be regulated. Generally, the higher the operating voltage, the poorer the regulation. This relationship is readily apparent in a volt-ampere curve of a conventional voltage regulating device which inherently shows a slight slope away from the normal. This imposes a limitation on the devices ability to regulate; that is on its accuracy of regulation.

A further limitation of the conventional tube is created by the changes in pressure and temperature of the gas within the tube. Such changes in pressure and temperature also change the slope of the characteristic voltage regulating curve. In other words, the voltage will vary more with current changes. In the temperature and pressure range of conventional devices, increasing gas density generally causes the slope of the curve to become flatter, that is the slope decreases and vice versa. Changes in pressure and temperature will affect the gas density and, therefore, the current versus voltage relationship.

iidlhilii Patented Pillar. 30, 1955 When both the inherent slope of the volt-ampere curve characteristic and the shift of the curve caused by changes in gas temperature and pressure are taken into consideration, the best of the conventional corona regulators are considered to be operating at peak performance if they are capable of regulating to within plus or minus 2 percent of the nominal value. However, it is oftentimes desirable to regulate the voltage at a substantially constant rather than varying voltage over a wide range of current flow. Under these circumstances, the above described prior voltage regulating devices are unsatisfactory and incapable of accomplishing such regulation.

it is accordingly an object of the invention to provide a voltage regulating device which overcomes the difficulties encountered heretofore.

it is a further object to provide a voltage regulating system in which the magnitude of the voltage regulation is accomplished by selectively controllin the temperature of the electrode structure and/ or the gaseous media.

Another object of the present invention is to provide a voltage regulating system operative on both positive and negative corona.

In accordance with the present invention, it has been discovered that at elevated temperatures of the gas or electrodes of a corona discharge device, the electrode voltage remains substantially constant and the detectable voltage changes with changes of current fiow, as occur in conventional corona devices, are substantially diminished. Accordingly, it is proposed by the present invention to provide a voltage regulating device embodying a corona discharge created by an asymmetrical electrode arrangement in which the temperature of the regulating device is controlled so that the electrode voltage is maintained substaritially constant and independent of the current flow within the operating voltage range of the electrode. This is accomplished by the provision of an adjustable variable heating device which is arranged to heat the environs of the regulating device to achieve the desired normal voltampere curve.

As discussed above, this volt-ampere relationship is illustrated and characterized by a volt-ampere curve which is substantially normal to the volt co-ordinate. For the purpose of facilitating the description of the device, the volt-ampere characteristic will hereinafter be discussed in reference to this curve.

It has further been discovered that the operating range of a corona discharge voltage regulating tube may be changed to different levels by raising or lowering the temperature of the regulating device environs. To this end, the heating device for controlling the temperature of the voltage regulator of the present invention is adjustable over a wide range.

Further objects and features will hereinafter appear.

in the accompanying drawings, there are shown for purposes of illustration certain of many forms which the present invention may assume.

FIG. 1 is a view of a discharge tube constructed according to the invention.

PEG. 2 is a further embodiment for heating the active electrode.

Phil. 3 is a plot of a typical volt ampere curve at difrent temperatures of the tube.

PEG. 4 is a view of a simple voltage regulating system incorporating the tube of the present invention.

FIG. 5 is a second embodiment of the invention.

FIG. 6 is a graphic illustration of the volt-ampere curves obtained from a positive active electrode at different temperatures of the electrode.

Referring now to the drawings for a more detailed description of the novel corona discharge tube of the present invention as illustrated in FIGS. 1-4, there is shown a extending electrode 17 which serves as the active electrode. The active electrode 17'may be of a nickel iron alloy similar to the exterior envelope ill or any other suitable conducting material. The interior 19 of the envelope is filled with a suitable ionizing gas for forming the corona. The gas is enclosed within the envelope. It is particularly advantageous to operate the device at substantially atmospheric pressure, since such procedure greatly simplifies the problem of sealing. However, the device may be operated at other pressures equally satisfactorily.

The type of gas employed will vary in accordance with the demand or load conditions to which the regulating tube is to be applied. For example, where relatively large current flow is to be regulated, a gas such as nitrogen or hydrogen might be employed. Conversely, where relatively low currents are required for regulation, a gas such as ordinary air may be employed. In the event air is employed, the tube may be vented at It). When gas such as nitrogen is used, such venting will not be included, but since the gas may be filled at substantially atmospheric pressures, the sealing of the tube is not critical and the simplicity of the above described tube may be retained.

While the tube It! has been disclosed in the form of a concentric electrode arrangement, it is to be understood that it is susceptible to other geometric forms such as a wire to a plane, point to plane, point to sphere, or wire to wire arrangement. Of course, each of these arrangements requires some type of enclosure such as an envelope shown in FIGS. 1 and 2.

In accordance with the present invention, the voltage regulating and volt-ampere curve characteristics are regulated by the temperature of the tube. To this end, in the embodiment illustrated in FIG. 1, the temperature of the tube environs is determined by the heat generated by an external resistance wire 21 which encircles the circumference of the cylindrical envelope II. The resistance wire 21 is connected to one end of its terminal 23 to a suitable source of alternating current 24 and its other end 26 to a rheostat 25 for adjusting the temperature of the heating wire 21.

It has been discovered that the regulating voltage or operating range of the tube constructed in accordance with the present invention may be shifted by changing the temperature of the tube environs.

Hence, when it is desired to change the voltage regulating range of the above-described tube, the tube temperature is regulated by the rheostat 25 which controls the heat generated by the resistance wire 21 as more fully to be described below.

It has also been found that heating the entire unit of the regulating tube is not essential to achieve voltage regulation, but that only the active electrode need be heated to achieve the desired voltage regulating characteristics. This is accomplished as shown in FIG. 2 by connecting the terminals 23 and 26 of the alternating current source 24 and rheostat arrangement 25 to the terminals 29 and 31 of the center electrode 17. This arrangement has also been found eifective to achieve the desired steep volt-ampere curve characteristics at different voltage regulating ranges when the temperature of the electrode 17 is shifted.

The voltage regulation characteristics of a tube constructed and operated in accordance with the present invention is illustrated in FIG. 3.

The curves illustrated may be obtained from a tube structure comprising a center electrode 17 formed from ferro nickel alloy. The tube is vented to atmosphere by way of vent 16 such that air is employed as the gas. As shown in FIG. 4, the tube lltl is connected at the electrode terminal 29 to the negative terminal of an unregulated direct current between power supply 33 and load 35. In this manner, the tube is connected to generate a negative corona for regulating the voltage. Connected in series between the power supply 33 and the tube It} is a resistance R. The resistance R is selected so that the voltage drop across it, due to the flow of maximum corona regulator current, is equal to the difference between the power supply output voltage and the voltage across the regulator, Hence, as the load impedance decreases, thereby demanding more current from the system, the current from the regulator tube decreases, but because the regulator tube maintains a substantially vertical volt-ampere curve relationship, the voltage remains constant.

The unregulated direct current power supply is connected to loads requiring 30, 25, kilovolts and a resistor R selected for each of the loads, in accordance with the above described requirements, is also inserted into the circuit. With a load of 20 kilovolts, the temperature of the electrode is elevated to 1500 F. and as shown in FIG. 3, this temperature results in a substantially steep Volt-ampere curve A such that the load voltage is maintained substantially constant. As shown, similar steep volt-ampere curves B and C are developed for the loads.

requiring and kilovolts when the temperature of the electrode is adjusted to 1490 and 1300 F.

It should be noted that While the above temperatures result in achieving the desired volt-ampere characteristics in a tube as described above, in the event that tubes of different geometry, i.e., relative size of electrodes, or a different gas composition were employed, different temperatures would result in different regulating voltages and vice versa. However, the temperatures required to achieve the desired voltage regulating range of such tubes could be ascertained readily.

In the above described arrangement, the temperature of the regulator and thereby the voltage regulating range of the same is accomplished by the manual adjustment =of the rheostat 25. It is to be understood that manual means other than the rheostat may be employed.

In accordance with the present invention, the temperature of the regulating tube, that is either the gas or the active electrode 17, may be controlled by the provision of a feedback circuit which is operative to measure the load voltage variations from a predetermined constant reference voltage and automatically adjust the temperature of the regulating tube so as to compensate for such variation and maintain a substantially constant output voltage at the active electrode of the voltage regulator.

As shown in FIG. 5, the voltage regulator tube 10 is connected into the circuit parallel with the load similar to the arrangement shown in FIG. 4. Also, shunted across the load 35 between the voltage regulator lltl and load 35 is a feedback circuit comprising a voltage divider arrangement 41 including a pair of resistors 43 and 45 which are elfective to transmit a signal at the point 47 corresponding to the load voltage. The load voltage signal is then introduced into a comparator 49 which may be of any type well known to those skilled in the art and compared with a reference signal supplied by a reference device 51 which may also be of any type well known in the art. The reference signal is adjusted so that it corresponds with the constant load voltage required at the load. If an error is detected by the comparator between the signal from the voltage divider circuit 41 and the reference signal device 51, an error signal corresponding to the diiference between the desired and actual load voltage is generated.

The error signal is applied to an amplification system 53 including typically a conventional chopper amplifier 55 and isolation transformer 57 of which the secondary leads are connected to the terminal ends of the electrode 17. Other amplification means, such as mangetic amplifiers, are equally applicable. In this manner, the out put of the amplification system which is used to heat the active electrode 17 is adjusted accordingly to raise or lower the electrode temperature and thereby causes the regulating voltage to be readjusted.

As a further adjunct to the present invention, a voltage regulating device operating on a positive active electrode is employed. Normally, the use of a positive active electrode (positive corona) does not provide a sufficiently steep corona curve characteristic to Warrant the use of a positive corona connected voltage regulating device as a voltage regulating means. These typical volt-ampere curves of a positive corona at different temperatures are illustrated in FIG. 6.

In accordance with the present invention, the electrode or output voltage is maintained substantially constant by varying the temperature as the current changes. This is accomplished by the feedback circuit 4! illustrated in FIG. 5. For example, if the tube It) having the electrode arrangement and dimensions previously described is connected to generate a positive corona, that is to say, if the center electrode 17 is connected to the positive terminal of the power supply, the volt-ampere curves illustrated in FIG. 6 will be generated. Assuming that it is desired to maintain a constant voltage output of 20 kllovolts as shown by the vertical dotted line D in FIG. 6, it is evident that as the current increases, the temperature must correspondingly be increased.

This adjustment of the temperature of the acive electrode 17 may be accomplished readily by the feedback circuit which, as described above, includes the voltage divider circuit 41 for measuring the load voltage. The load voltage is then compared at the comparator 49 with the reference signal which is set at the desired load voltage from the reference device 51 such that the output of the comparator 4% is effectively a signal corresponding to the load change. Hence, if the load is greater or less than the desired load, the signal is suitably amplified by the transformer coupled stage of amplification 53 such that a greater or lesser flow of current corresponding to the signal passes through the electrode 17. This increase or decrease of current flow, of course, causes the temperature of the electrode 17 to increase or decrease a corresponding amount. As illustrated in FIG. 6, upon an increase in temperautre of the center electrode 17, the

output thereof is decreased and conversely, when there is a decrease in temperature, there is an increase in output voltage. It should be readily apparent, therefore, that the feedback circuit is effective to maintain automatically the output voltage substantially constant as illustrated by the dotted line curve D.

What is claimed is:

1. A voltage regulating system including an unregulated supply of direct current for supplying a load voltage and means for maintaining said load voltage constant, said maintaining means comprising:

(a) an envelope filled with a gas at substantially atmospheric pressure,

(1) said gas being ionizable under large voltage gradients,

(b) electrode means disposed in said envelope for forming a corona discharge,

(c) means operatively connected to said electrode means for heating the gas in said envelope to a selected elevated, substantially uniform and substantially constant temperature and (d) means operatively connected to said heating means for selectively varying the temperature of the gas in accordance with the load voltage demand thereby maintaining said load voltage substantially constant.

2. The invention as defined in claim 1 in Which said temperature varying means is operatively associated with said load and said heating means to automatically vary the temperature in response to load changes.

References Qited by the Examiner UNITED STATES PATENTS 2,489,891 11/49 Hull 3l3-212 X 2,502,331 3/50 Malter 3l*212 X 2,791,716 5/57 Friedman 313-216 X 2,841,758 7/58 /Vright 32322 2,980,819 4/61 Feaster 313-2l2 3,124,744 3/64- Zito 324-33 LLOYD MCCOLLUM, Primary Examiner.

MILTON O. I-lIRSHFIELD, Examiner. 

1. A VOLTAGE REGULATING SYSTEM INCLUDING AN UNREGULATED SUPPLY OF DIRECT CURRENT FOR SUPPLYING A LOAD VOLTAGE AND MEANS FOR MAINTAINING SAID LOAD VOLTAGE CONSTANT, SAID MAINTAINING MEANS COMPRISING: (A) AN ENVELOPE FILLED WITH A GAS AT SUBSTANTIALLY ATMOSPHERIC PRESSURE, (1) SAID GAS BEING IONIZABLE UNDER LARGE VOLTAGE GRADIENTS, (B) ELECTRODE MEANS DISPOSED IN SAID ENVELOPE FOR FORMING A CORONA DISCHARGE, (C) MEANS OPERATIVELY CONNECTED TO SAID ELECTRODE MEANS FOR HEATING THE GAS IN SAID ENVELOPE TO A SELECTED ELEVATED, SUBSTANTIALLY UNIFORM AND SUBSTANTIALLY CONSTANT TEMPERATURE AND (D) MEANS OPERATIVELY CONNECTED TO SAID HEATING MEANS FOR SELECTIVELY VARYING THE TEMPERATURE OF THE GAS IN ACCORDANCE WITH THE LOAD VOLTAGE DEMAND THEREBY MAINTAINING SAID LOAD VOLTAGE SUBSTANTIALLY CONSTANT. 